I recently purchased a 1979 Islander 28. The comression post has sank / crushed into the floor.It has dorped a little over a half an inch. I was thinking of letting the turnbuckles out to realease tension, then jack up the compression post.Shimming it up with aluminum plate or fiberglass.
Is this a Dumb idea? I Would appreciate any advise, or info.

Do you know why it compressed? Was it the floor that failed and pushed downwards, is there a visible deformation of the hull under the water at that zone?

Or was it the post that shrank with the weight.

Absolutely yes, do repair with a shimming piece, but if you can, make a new compression post. I assume it's wood correct? Just make sure the shims are correctly secured and attached eithr to the post or the hull, so they don't come off as you sail and drop the mast all of a sudden which will cause a failure.

I have a 1979 i28. We are almost complete with that and additional structural repairs.

The Compression post may shrink a bit, ours was about a 1/16" to 3/32 shorter than the bulkhead it is attached to. The real problem is too much load on an improper material, i.e. the 3/4" plywood cabin sole.

On our boat the post loads down on top of the plywood cabin sole and crushes it, we had a bit more than 3/8" squeezed out of the sole and a slight deformation on the tops of the floors the sole rides on. I believe it totaled about 1/2" "crushed out".

On the i28 I race on, they had installed a plate as a repair. When they adjust backstay tension they still pull until the head door almost jams...

First off, how about a more details regarding your boat, like do you have a teak cabin sole or just the plywood and carpet...?

Do you know why it compressed? Was it the floor that failed and pushed downwards, is there a visible deformation of the hull under the water at that zone?

Or was it the post that shrank with the weight.

Absolutely yes, do repair with a shimming piece, but if you can, make a new compression post. I assume it's wood correct? Just make sure the shims are correctly secured and attached eithr to the post or the hull, so they don't come off as you sail and drop the mast all of a sudden which will cause a failure.

GIULIETTA,

Yeah it looks like the plywood sole was softer than the compression post, and it "crushed" into the sole. There is no sign of rot at all. As far as the make up of the compression post... it's a two piece. The top half looks to be made of steel, the bottom half is wood.
I can't get the jack directly centered under the mast, but what I plan to do is loosen the turn buckles a little at a time and jack up the post / mast, and shim it with some aluminum plate. (I will take your advise and secure the shim, thanks). I think it is a feasable plan. We do not have crane service or drydock facilities yet, so I'm trying to address the issue in the water.
Your reply is very much appreciated, if you think of anything else let me know.

I have a 1979 i28. We are almost complete with that and additional structural repairs.

The Compression post may shrink a bit, ours was about a 1/16" to 3/32 shorter than the bulkhead it is attached to. The real problem is too much load on an improper material, i.e. the 3/4" plywood cabin sole.

On our boat the post loads down on top of the plywood cabin sole and crushes it, we had a bit more than 3/8" squeezed out of the sole and a slight deformation on the tops of the floors the sole rides on. I believe it totaled about 1/2" "crushed out".

On the i28 I race on, they had installed a plate as a repair. When they adjust backstay tension they still pull until the head door almost jams...

First off, how about a more details regarding your boat, like do you have a teak cabin sole or just the plywood and carpet...?

Paul Comte
i28
Milwaukee WI

Thanks for the reply Phil. My boat is a 11979 I28 as well. The sole is plywood, and the problem is identical to what you described. We do not have crane or dry dock service back yet so I'm trying to address this issue in the water. I can't get the jack directly centered under the mast, but I think it will be ok.

We had a '78 Islander with the same problem. I loosened all the turn buckles and got a jack in there. I put the jack across one of the stringers a little further aft and then I got in there with a sawz-all and cut out the compressed plywood floor. I cut the flooring away about half the width around the two adjacent stringers then I took a two inch thick piece of maple plank I had and cut that down to size to it would slide in under the compression post with the two plank ends carved down so it would rest on the stringers then epoxied the whole thing in. I sold the boat a while later, so I don't know how well the repair held up over time, but it did the trick in the short run.

I am close to purchasing a 1978 Islander 28 which I think has some related issues. My surveyor found rotting plywood in the bilge at the lower end of the baffles that becomes structure for the floor and one which the mast compression post bears on. My surveyor thought it wasn't super major b/c there was plenty of solid wood where it was needed, but thought it needs to be fixed. The owner offered to make it right and cut out the rotting portion of the plywood and glass in new. I also noticed where the metal compression post has deflected the wood trim it bears on before tranfering its load to the compression post in the head.

Have any insights or thoughts? How concerned should I be with this? Is this a bigger issue than just replacing rotting plywood? Is it likely that the cabin sole is crushed under the post as well - indicated by the deflection?

Its always wise to remove any and all compromised wood when doing any repair if you can...sometimes it isn't critical if it is not structural ( usually if plywood is in a fiberglass boat it is for structural/stiffening reasons) and other means then can be used as a quick fix temporary fix..but if you take the effort and time to replace it you will feel better about it and so will the future surveyor and buyer.

As far as how big of a job it is ..that's hard to say depending on your boats configuration...the actual repair is usually way easier then the tearing apart and reassembling of everything to get at it.

Relationships are everything to me..everything else in life are just tools to enhance them.

The purchase price of a boat is just the admittance fee to the dance...you still have to spend money on the girl...so court one with something going for her with pleasing and desirable character traits others desire as well... or you could find yourself in a disillusioned relationship contemplating an expensive divorce.

Thanks for your reply. We are getting all the bad wood out and replacing with new. As far as I can see.... it might be better than when it was new. Seemed to be a small design flaw or manufacter overlook. The plywood ribs dipped into the bildge and the bottom end grain was exposed to bilge water and allowed water to seep into the wood.

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